System for energizing electrical precipitators and the like



Jan. 19, 1954 R. E. WILLISON 2,566,496

SYSTEM FOR ENERGIZING ELECTRICAL PRECIPITATORS AND THE LIKE 2 Sheets-Sheet 1 Filed Sept. 6, 1951 murtkuuwb INVENTOR RALPH E. WILL I SQN ATTORNEYS Jan. 19, 1954 R. E. WILLISON 2,666,496

SYSTEM FOR ENERGIZING ELECTRICAL PRECIPITATORS AND THE LIKE 2 Sheets-Sheet 2 Filed Sept. 6, 1951 RALPH E. WILLIS-ON ATTORNEYS iatented Jan. 19, 1954 rem OFFICE SYS TEM: FORENERGIZING ELECTRICAL; BRECIPITATORS ANDLTHELIKE ,North Branch v N. .L, assignor. to Research Corporation; New-York; N2

corporationof NewYork Applicationrseptember s, 1951-, se iarmsziazso (or: sm-7 Y 8 Claims;

This invention. relates..,toa system. ,for energize ing the. electrodes. otjan. electrical precipitatorand thelikeof the type disclosed in the application of Herbert J. Hall, Serial No. 169,019.; filed. June 19, .1950, for System for. Energizing, Electrical Precipitators." More particularly, this inven: tion relates to a, system in which the. voltage ap; plied to theelectrodesof the precipitator isauto: matically regulated to provide...a-predetermined rate ofjsparking betweenthe electrodes.

In the operation of electrical.precipitators, contrary to previously. accepted 'ideas,.it. h'asbeen foundv that. optimum performance is attained when.the.-voltage.between the electrodes of the precipitator is maintainedat aval-ue 51113563111. tially higherthan that .at, which sparks start to jump. between the electrodes. The, sparks re.- ferred to are not the disruptive power arcs that sometimes .occur between the ielectrodes,.but are sparks of relatively low power that occur more or less frequently, dependingupon operating conditions, and that do not'put suddenserious. overloads on the energization system. In, an electrical precipitator, there is an optimum rate ,of sparking above and'b'elow which collection efliciency declines. Although the optimum sparkingrate will vary 'Qr difierentprecipitators, it typically is of the orde of fiftyto one hundred sparks per minute per precipitator section.

An object of the inventi'onris to provide a system for energizing the electrodes. of electrical precipitators that automatically sets and holds the voltage at a value correspondingrto substantially optimum; sparking rate.

Another object is to provide a relatively simple control system 'for' automaticallyregulating voltage.

Another object is to provide in. such a control system a device-that counts each inter-electrode spark to form the basis for-control.

These and other objects and "advantages of the invention are typicallyachieved'in asystemt-for energizing the electrodes of an electrical "precipitatorand the like including ,a voltage. regulator, a device responsiveto disturbances inxthe system caused. by an intereelectrode spark, meansior generating current pulses in accordance-withthe responses of the, spark.responsive.device, motor meansactuated by the current pulses, a rate motor. operable at a. .preselected speed,.. means including. a pairof. cooperating relatively movable members providing. a control signalin. accordance with. differential, movement oi the members, .one or the .members beingdriven by themotor means and the other of the members beingdrivenbythe 2 rate motor. and-meansv applyingnthe control sig: rial-to. the voltage. regulator. to vary the voltage thereof; The means providing the control signal may take a varietyof forms and may include a mechanical differential gearing, ,a synchro-generator, a potentiometer or the like.

The. inventionwill be described with greater particularity, and other of its objects and advantages will'bepointed out in the followingjdetailed description or the several exemplaryembodiments shown in the drawings.

In the drawings:

Fig,..l,ls, a diagrammatic .view of one form of automatic, voltage controlsystem in accordance with the invention;v

Fig. 2, is a diagrammatic view of a portion of the, system shown in Fig. l and including limit switch devices;

rig.v 3 is a, diagrammatic view of a portion of anotheixfo'rmof automatic voltage control system; and

Fig. 4 isa diagrammatic view of a portion: of another such system.

Referring to the drawings, particularly to Fig. 1,; the. automatic voltage control system shown includes-an electrical precipitator lil,'having a collecting, electrode H and a"complementary. disfchargefelectrode l2. Theprecipitator is energized iroma source of current represented bythe AC generator l3 feeding the line L17-L2. A switch 14 connectsthe line Lr-Lz to the winding [5 of a. variable autotransfo'rmer [6 having a variable output tap Hand 2. fixed .output'terminal l8. Thefiutput of the autotransformer is applied to theprimarywindingl 9 of a step-upv power trans,-

former 20 through a surge controlling resistor 2|. HighitensionAC from the secondary winding,22 f..the powerv transformer is rectified in ,a-con ventional rectifier 23 and the unidirectional. pulsating .current output of the latter is applied to the .lprecipitator electrodes through. a .high tension cable 24 and ground connections .25 and .26.

Sparks that jum between the. electrodes. H and I2 are sensed in' any convenient way, as by a. sensing device 27 capacitivel-y related to the hightension cable 2,4,.- Each spark. causes a dis turbancein the cable 24 that registersaas a voltage change in the, sensing device 21.

A glow tube 28, which may be .a strobotron qr .thyratron, is connected to the-capacitivesensing vdevices?.thrugh a shielded a le -Z9 an l-..-a;cou-

plingenetwork ,including the condenser 30 and resistor 3|. The glow tube has a cathode ;3 2, =,a.-first grid-.33., a,second or control-grid ill-and an anode gridv being connected-;to ,the

and 59.

'nection being accomplished by 'designated 15. Energization of the winding 61 "turns the rotor 65 in the opposite direction to effect a decrease in the output voltage of the autotransformer.

the-electrodes of precipitator I0.

aeecaee Resistors 35, 3! and 38 provide the required bias for the glow tube grids. A firing condenser 39 is connected across the anode and cathode elements of the glow tube.

A pulsing condenser 40 is connected across the firing condenser 39 through the winding 4| of a solenoid device 42 and a battery 43 or other source of direct current is connected across the pulsing condenser 4t through a switch 44.

The solenoid device 42 includes a movable core or armature 45 having a push rod 45 engaging the periphery of a ratchet wheel 41. A spring 48 is engaged between the collars 49 on the push rod and is anchored to a base 55. Energization of the winding 4| of the solenoid device draws the armature 45 and push rod 45 to the right against the force of spring 48 a distance sufficient to allow spark sensing device.

the push rod to engage a tooth of the ratchet.

wheel 4'! that is next adjacent to the tooth ongaged when the solenoid is deenergized and at rest. Upon deenergization of the solenoid, the spring returns the push rod 45 to the left thus advancing the ratchet wheel one tooth in the counterclockwise direction. The ratchet wheel is advanced in this manner each time the solenoid 42 is energized and deenergized.

The ratchet wheel 4'! is connected through a shaft to one input shaft 52 of a mechanical diiierential gearing 53. The other input 54 of the differential gearing is driven at a preselected speed by a rate motor 55 energized from a source of current 55 through a switch 51 and wires 58 The speed of the rate motor is controlled by a potentiometer '60. Output shaft 5| of the differential gearing drives a cam 52 of a switch 53 controlling a reversible motor 54 that varies the output voltage of the autotransformer Reversible motor 54 has a common terminal 55 that is connected to one end of each of the windings 65 and 51 of the motor and through the conductor 68 to one side of the current source 55. When winding 66 is energized, the rotor 69 turns in a direction to move the tap I"! to raise the output voltage of the autotransformer 16, such cona shaft or linkage Terminal ll of the reversible motor, which is connected to the winding '56 and may be termed the raise voltage terminal, is connected to one contact point iii of the switch 63 and terminal 15, the lower voltage terminal or the motor, is

connected to contact point 14 or" the switch 63.

An arm 15, pivoted at 15 has a follower ll riding on the cam 52 and carries a contact point 18 that closes with contact point #2 when the cam is turned to bring the rise 19 under the follower. When the points l2, 18 are thus closed, the raise 'voltage winding 65 of the reversible motor is energized through the switch 63 and the con- "ductor 85.

Another switch arm 8| having a contact point '82 cooperating with the point 14 energizes the 'lower voltage winding 61 of the reversible motor when the switch cam 62 is rotated to close the switch points 74, 82.

An auxiliary, manually operable switch 83 is employed for manual setting of the output voltage of autotransformer l6 through reversible motor 64.

closed and the setting of autotransformer I6 is adjusted by operation of switch 83 to provide an output voltage producing substantially optimum sparking rate in the precipitator.

Each spark is sensed by the pick-up device 21 and each spark fires the glow tube 28 discharging the firing condenser 39 through the glow tube. After each discharging of the firing condenser, the latter is recharged from the pulsing condenser 45 and battery 43, the switch 44 being closed. The recharging pulse passes through the solenoid winding 4| energizing the solenoid to move the armature 45 to the right. Upon subsidence of the pulse, the spring 48 returns the armature to the left and advances the ratchet wheel 41 one tooth. It is thus seen that each inter-electrode sparks results in an advancing movement of the ratchet wheel 41 and that the rate of rotation of the wheel is proportional to sparking rate.

Under conditions of optimum sparking, the speed of rate motor 55 is adjusted by potentiometer 55 to counteract the effect on the differential gearing 53 of the rotation of shaft 52 effected by rotation of the ratchet wheel 41, and the output shaft 6i of the differential gearing remains stationary. The cam 52 of switch 63 remains in its neutral position as seen in Fig. 1 and no adjustment of the autotransformer is made.

If the sparking rate falls below optimum, ratchet wheel 41 turns at a correspondingly slower rate and the output shaft SI of the differential' gearing rotates the switch cam 62 to close switch points 12, I8 and energize the reversible motor 54 in a direction to raise the output voltage of the autotransformer It. The voltage impressed on the electrodes H and I2 of the precipitator is thus raised to increase the sparking rate to slightly above optimum. The speed of ratchet wheel 41 is correspondingly increased and the diiierential output shaft 6| rotates in a direction to open the switch points 1'2, 18 to stop the reversible motor.

If the sparking rate should rise substantially above optimum, a reverse action takes place.

The speed of ratchet wheel 41 increases, switch raise voltage and lower voltage switches and completely vitiating the control action of the system. A mechanism for limiting the rotation of switch cam 52 is shown in Fig. 2.

Referring to Fig. 2, the differential gearing output shaft 6| operates the cam 62 of the rotary switch 63, as in the system shown in Fig. l. Shaft 61 carries a second cam 84 that has a depressed portion 85 that opens a switch 86 when shaft Bl rotates in the clockwise direction from the position shown in Fig. 2. switch 86 is open, the rate motor 55 is deener- When the gized. Shaft 5| carries a third cam 81 having 'a depressed portion 88 that opens a switch 89 when the shaft rotates 90 in the counterclockf'wise direction from the position shown in Fig. 2. 75 When switch 89 is open; the spark counting device is inoperative.

acetate Inoperation; if the rate motor SS should an. the control device would appear to call for a lowering of the precipitator energizing voltage. Shaft BI would turn in a counterclockwise direction untilswitch-BS is opened by cam 81 and the spark counting system would be deenergized; Conversely, if the sparkcounting system should fail, the control device would appear to call for an increase in precipitator energizing voltage. Shaft GI would turn in a clockwise direction until cam 84 opens switch 86 thus deenergizing and stopping the rate motor. Theapparatus of Fig. 2 is seen to prevent continuous rotation in one direction of the cam 62 of switch 63.

In Fig. 3 is shown a portion of another form of voltage control system using a differential arrangement for comparing sparking rate with a preselected standard and employing electrical phase shifting principles to effect control.

A synchro generator having a-first rotor element 99 and a second rotor element BI is mounted in bearings so that the first rotor 90 is rotatable in the bearings and-the second rotor is rotatable with respect tothefirst rotor. The generatorhas a single-phase first rotor and a two-phase second rotor. Connections to S1, S2; r1, r2; r3, and-r4 are made-through slip rings. The first rotor is rotated at a constant speed by a rate motor 55 and driving shaft 52, the speed'of rotation'being proportional to the desired sparking rate. The second rotor 9I is mechanically driven by the output shaft 5| of a spark converter 93 that includes a motor driven'at a speed proportional to actual sparking rate such asthe motor having the ratchet wheel 41 of Fig. 1.

Power for excitation of the phase shift comparator 95, 9| and-controller to be described is supplied by a transformer 94 having a primary winding 95 supplied with alternating current from aline 96', 91. One secondary winding 98 supplies a phase referencesine wave voltage to the winding of thefirst rotor 99 of the synchro generator. The second rotor 9 I, whose windings are physically displaced 90, has a resistor 99 and a condenser IIlIl connected in series between the-points 1'1 and re: The electrical output of the second rotor is taken from the points T2 and 14. The rotor output is a sine wave voltage of constant amplitude, the phase of which is shifted ahead of or behind the phase reference input to the first rotor 99 depending on the speed of the rotor relative to the speed: of the stator. The average amount of phase shiftin the synchro output is proportional to the deviation in the actual sparking rate, as reflected in second rotor speed, from the desired sparking rate, as reflected in. first rotor speed.

A thyratron ill I, having the usual cathode I02, gridtlfiti and anode I94, .is-energized in the anodecathode. circuitfrom a. secondary winding I05 of the transformer 94. Included in the anodecathode circuit is a series connected solenoid coil I08 having a cooperating armature I01. Movement of the armature operates a switch designated by the general reference numeral I08. The switch bar I99 is pivoted at III] and is provided with contact member III and H2 cooperating respectively with complementary fixed contact members II 3 and I I4. A tension spring I I5 urges the contact member H2 downwardly and energization of the solenoid coil urges the contact member I II downwardly through the action of armature IE1! on the switch bar I09.

The switch I08 controls the action of a reversible motor such as the motor 64 of the systern of Fig.1 to raiseand lower'the pre'cipita-tor' energizing voltage. The line I- I-lr, I'I'I is con= nected to a source of current (not shown). Conductor II'l is connected to the commonterm-inal of the reversible motor. Conductor II6-is connected to the switch bar I09. Contact member II3 of the switch is connected through' a wire I I8 to the raise'vo'ltage terminal ofthe reversible motor-and contact member H4 is connected to the lower voltage terminal through a wire H9; Itis thus seen that when the switch con-' tacts II 5, 3 are closed, the reversible motor is energized to raise the precipitator voltage and when the contacts II2, II-tare closed, the-re=- versible motor is energized to lower the precipitator voltage.

Bias for the grid I03 of the thyratron IIlI is provided by a-battery I20 and potentiometer I2I' in the cathode-grid circuit;

It will be seen that in the circuit of Fig. 3 the amount of direct current that passes through the thyratron 113i and solenoid winding I06 depends on (a) the D. C. bias on the thyratron'grid as applied by the battery i2il and (b) the phase of the phase shifted signal applied to the grid circuit relative to the phase reference voltage in the plate circuit. The smoothing of control action depends on the relative amplitudes of the A. G and D. C. voltages applied to the thyratron grid.

When the second rotor 9 I of the synchro generator is turning faster thanv the first rotor 9|), thus indicating a higher sparking rate than is desired, the current in the plate circuit of the thyratron increases, the armature illl is drawn downwardly, and switchcontacts II2, H l are closed to effect a lowering of the. precipitator voltage. Cone s y, when the second rotor-9i is turning slower than the first rotor all, current in the plate circuit of the thyratron decreases and the spring IIii closes switch contacts II-I-', II3 to-effect an increase in the precipitator voltage.

Another form of control device is shown in Fig. 4. This device issimilar to that shown in Fig. 3 except that a differentialpotentiometer is sub stituted for the synch-ro generator of the'device of Fig. 3 and changes'necessary to the substitution are incorporated in the apparatus'of Fig.4.

A potentiometer, designated by the general reference numeral I22, of the well known circular type, having a resistance element F23 and a slider I24, and terminals I25; I26 and I27, is mounted in bearings so that the case and the enclosed resistance element and slider are rotatable about the axis of the slider while the. slider is independently rotatable on its own axis. The case and resistance element are driven by a rate motor 55 through the shaft 92' and the slider is driven in the same direction by the spark converter 93" through the shaftfii The terminal I26 of the resistance element is grounded through a slip-1 ring connection and the other terminal I25 of the resistance element is connected to one pole of a battery I28 through a slip-ring connection. The other pole of the battery is grounded. Slider I24 is connected to the upper end of solenoid coil I06 through a slip-ring connection, and the lower end of the solenoid coil is grounded. It will be seen that the amount of current flowing through the solenoid coil depends upon the position of the slider I 24 on the resistance element I23 of the potentiometer which, in turn, depends on the relative speeds of shaft 92 (proportional to the desired rate of sparking) and shaft 5| (proportional to the actual rate of sparking). As the current in solenoid coil I06 increases, the lower voltage? contact members IIZ, Ht are closed because of the pull of armature I07 on the bar of switch I08. As the current in the solenoid coil decreases, the raise voltage contact members I I I, I I3 close due to the pull of spring I I.

These control conditions are brought about by differences in rotational speeds of the cooperating resistance and slider elements of the potentiometer I22. When the slider rotates faster than the resistance element, indicating a sparking rate above optimum, the slider advances towards terminal I25 of the resistance element and increased current flows through the solenoid coil I05. The contact members H2, H4 are closed and the precipitator energizing voltage is lowered. Conversely, a sparking rate lower than optimum causes the slider I24 to move towards the resistance element terminal I26, current in the solenoid coil I26 decreases, switch contact members Iii, I I3 close, and the precipitator energizing voltage is raised.

From the foregoing description, many modifications of the invention will occur to those skilled in the art without departing from the invention as defined in the claims. a

It will also be seen that the present invention provides a system that automatically controls the energizing voltage of an electrical precipitator or the like in accordance with the departure of the sparking rate from a preselected rate.

I claim:

1. A system for energizing the electrodes of an electrical precipitator and the like compsing a voltage regulator, a device responsive to sturbances in the system caused by an inter electrode spark, means for generating current pulses in accordance with the responses of said spark responsive device, motor means actuated by said cur rent pulses, a rate motor operable at a preselected speed, a motor for varying the voltage or" said voltage regulator; and differential drive means for energizing said motor driven by said motor means and said rate motor.

2. A system as defined in claim 1 wherein said differential drive means includes a mechanical differential gearing.

3. A system as defined in claim 1 wherein said differential drive means includes a synchro-generator.

4. A system as defined in claim 1 wherein said differential drive means includes a potentiometer the resistance element and slider of which provide the relatively movable members thereof.

5. A system as defined in claim 1 wherein said differential drive means includes a, mechanical differential gearing driving a rotary electrical switch and including means limiting the rotary movement of said switch.

6. A system for energizing the electrodes of an electrical precipitator and the like comprising a voltage regulator, a reversible electric motor connected to vary the voltage of said regulator, switch means controlling said reversible electric motor, a device responsive to disturbances in the system caused by an inter-electrode spark, means for generating current pulses in accordance with the responses of said spark responsive device, a rotary electric motor actuated by said current pulses, a rate motor operable at preselected speed, and a mechanical differential gearing having two input shafts and an output shaft, said rotary electric motor being connected to drive one of the differential input shafts, said rate motor being connected to drive the other of said input shafts, and the output shaft of said differential gearing being connected to operate the switch means controlling said reversible electric motor.

7. A system for energizing the electrodes of an electrical precipitator comprising means for varying the voltage applied to said electrodes, a device responsive to disturbances in the system caused by an inter-electrode spark to continuously integrate the occurrences of said disturbances with respect to time to produce a control force which is a function of the continuous rate or" production of said sparks, a control device operatively connected to said voltage varying means and to said disturbance-responsive means to vary the control action thereof in accordance with the value oisaid control force and therefore in accordance with the current integrated rate of said pulses.

8. ,A method of energizing the electrodes of an electrical precipitator to produce an optimum sparking rate comprising sensing disturbances in the system caused by an interelectrode spark, continuously integrating the occurrences of the sensed disturbances with respect to time to produce a control force which is a function of the continuous integrated rate of production of said sparks, varying the voltage applied to said electrodes in accordance with the value of said control force so as to maintain the pulse rate at an optimum value.

RALPH E. WILLISON.

References, Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,050,367 Myhre Aug. 11, 1936 2,162,501 Draper June 13, 1937 2,239,768 Artzt Apr. 4, 1941 2,297,740 Brown Oct. 6, 1942 2,297,841 MacKenzie Oct. 6, 1942 2,623,608 Hall Dec. 30, 1952 FOREIGN PATENTS Number Country Date 670,245 Germany Feb. 18, 1932 

